A coupler device may be used for, but is not limited to, connecting and de-connecting conduits intended for transfer of pressurized fluids, such as hydrocarbon-containing fluids. Typically, such a coupler device will be used for offloading crude oil or gas from the stern of a floating, production, storage and offloading (FPSO) unit to a shuttle vessel. One part of the coupler device will typically be installed on the shuttle vessel, while another part is carried on the FPSO unit.
Coupler devices using clamps and connector hubs are extensively used for connecting conduits carrying pressurized fluids. These coupler devices include connector hubs on the ends of the two tubular fluid conduits to be connected. Each connector hub has a flat inner face with a seal ring groove in the face. The opposite, outer side of each connector hub has an inclined annular surface. The inclined annular surfaces mate with inclined annular surfaces on a clamp that can force the faces of the two connector hubs axially into engagement and, at the same time, move the seal ring grooves in each face into sealing engagement with a seal ring. Bringing the faces of the two connector hubs into engagement gives the connection structural stability. Clamps and connector hubs provide an alternative to standard flange connections.
Due to safety reasons and for efficiency of operation it is desirable to have a coupling and decoupling process of the connector hubs that is both quick and reliable.
There is a range of prior coupler designs using clamps as coupling means for coupling pipe conduits, where the clamps use bolts as tightening/pre-tensioning means. These couplers are mainly used for permanent connections, and auxiliary equipment for handling these couplers is required. The large bolts generally require large and heavy pre-tensioning equipment.
Coupler devices using clamps and connector hubs are generally designed for manual make up. Clamps for high pressure and large bore conduits are typically large, heavy, and difficult to handle, and it is challenging to obtain an even pressure distribution between the clamp and the connector hubs. Such coupler devices generally are also quite time consuming to make up, requiring special handling tools. Both the bolts and the tensioning equipment are typically large and heavy, as well as expensive.
Coupling devices with clamps for connector hubs with integrated valves are getting even larger due to the larger diameter required for housing the valve equipment. Auxiliary equipment is then required to handle the clamps, and the heavy bolts require special and large equipment for pre-tensioning. This is especially a handicap for coupler devices assigned for repeated coupling and decoupling during operation, and especially for operations where time is crucial.
U.S. Pat. No. 3,403,931 discloses a coupler device with two segmented clamps bolted together by two sets of two bolts. The two segmented clamps grip around conically shaped connector hubs. The two hub connectors are pressed towards a seal ring therebetween when the bolts are tensioned up.
Clamps with one bolt in each end are disclosed in U.S. Pat. No. 4,611,839.
U.S. Pat. No. 4,725,080 discloses a coupler device for remote assembling and disassembling a Grayloc® type connector between a pipe and a closure for the pipe. This coupler device uses one hydraulic actuator for each of two clamping members for moving the clamping members into contact with respective connector hubs. Clamping rods are bolted onto the clamping members. Further, one stud tensioner is provided for each clamping bolt for rotating the clamping nuts. The stud tensioners operate by applying torque to the nuts. The stud tensioners themselves, along with sleeves, are moved into position by another actuator. It is not disclosed how the stud tensioner engages the nuts. The tensioners and sleeves are guided by some means as the clamps are moving toward the hub.
U.S. Pat. No. 5,443,581 describes a coupler device with clamp and connector hubs incorporating a flat adapter ring arranged between the two connector hubs. The adapter ring has tapped holes holding one stud bolt extending outwardly through openings in each of the clamp segments, and with nuts on the outside of the clamp segments for pressing the clamp segments towards the connector hubs into connected position. This arrangement is especially designed for hub connections stacked in a vertical axis, such as in blowout preventers. A drawback with this solution is that the clamp is unstable when supported by one rod only during the idle conditions prior to connect up. Further, such an insert ring will not have substantial anchoring for supporting heavy weights prior to connect up. The insert ring may be troublesome to insert in cases where the pipe line is arranged horizontally, and the handling problems with the clamps will be much the same as for standard clamps without the rods. The connector hubs have flat mating faces throughout the pipe section leaving all the centralizing and shear loads to be handled by the seal rings. Such seal rings may thus easily be damaged during mating operation, and they will only offer a centralizing effect during the last few millimeters prior to “touch down”—and offer no assistance to control of the angular deviation. Such an insert ring requires two sealing surfaces yielding one additional potential leakage source.
U.S. Pat. No. 7,891,713 B2 describes a coupler device using clamps hinged in one end and pre-tensioned by one bolt in the other end. It is not revealed if the clamps are fixed to the pipe. This coupler device is representative of various versions of ring type clamps, and requires either more than two clamps and/or clamps with complicated geometry as described in said patent. One of the problems with this type of coupler device is free axial access for the connector hub part of the pipe to be connected. The ring type clamps require room over a full 360°, leaving no room for other equipment such as valve actuating means required for quick release couplers where valves are required close to the interface section. Another challenge with this coupler device is to keep the clamps at a correct axial position relative to the connector hubs during coupling. The forces in the pivoting links are huge compared with the requirement to keep those links moderately sized. At disconnect, after an extended time in operation, the clamps may get stuck and may be hard to release.
The above mentioned prior art coupler devices mainly utilize torque control of bolts for pre-tensioning the connector hubs and the connection faces. According to general uncertainties regarding setting a correct design friction coefficient, there will correspondingly be an uncertainty as to how large the actual preload of the coupler device will be when made up.